Human productivity and quality of life has been substantially increased in recent years by the use of efficient climate control equipment, such as air conditioning. The growing demands for food preservation on the one hand and energy-saving requirements on the other hand could be satisfied only with effective and economical thermal control systems. There are existing refrigeration systems which consist of a refrigerant vapor compressor discharging into a condenser which liquefies the refrigerant while it emits heat to the surroundings. This is followed by partially vaporizing the liquid refrigerant and lowering its temperature by means of absorbing its latent heat of vaporization. The refrigerant then passes through the evaporator which vaporizes the remaining liquid and absorbs the heat from the cooling object. The produced vapor then returns to the compressor to repeat the cycle again. The circulation of the thermotransfering materials such as a refrigerant through the evaporator makes the process of absorbing heat from the cooling object more efficient.
Suitable forms of jet pumps for the circulating refrigerant are comprised of a suction inlet for entering liquid which is then lifted by the pump into the mixing chamber, a jet with an inlet for the introduction of high-pressure liquid. The high-pressure liquid, called working liquid, flows into the mixing chamber and creates a suction effect at the suction inlet. The low-pressure liquid, called secondary liquid, is lifted by the pump and sucked into the mixing chamber.
An early example of a jet pump is disclosed in U.S. Pat. No. 607,849 by Hampson in 1898. Subsequently, multiple attempts to increase efficiency of conventional jet pumps for refrigerating systems were made. For example in the U.S. Pat. Nos. 3,199,310 by Schlichting, 2,301,839 by Work, and 3,277,660 by Kemper disclosed the idea of using different liquids as secondary and working liquids to increase the efficiency of the jet pump. In U.S. Pat. No. 3,680,327 by Stein disclosed a "compound ejector" for use in steam-jet refrigeration that introduces multiple primary jets through stationary nozzles in order to mix secondary and working liquids. In U.S. Pat. No. 4,378,681 by Modisette, U.S. Pat. No. 4,748,826 by Lauman, and U.S. Pat. No. 5,647,221 by Garris, Jr. are disclosed the idea of using virtual flow for increasing the efficiency of a jet pump or an ejector.
It is known that heat loading on the cooling system during the refrigeration or freezing process is variable and the quantity of the refrigerant circulating through a freezer or a refrigerator changes to large extent throughout the process. The greatest quantity of the refrigerant circulates at the beginning of the process. Some time later, the quantity of the refrigerant must be reduced due to the decreasing amount of heat transferring from cooled object and refrigerant. The final step of the process requires further reduction of the feeding refrigerant. Obviously, the optimum process should allow adjusting the quantity of the feeding refrigerant according to the amount of heat exchanged.
All of described types of the jet pumps have a constant cross section of the nozzles. Therefore they can not change the quantity of a refrigerant introduced into an evaporator and thus cannot reduce the time of the refrigeration process. Accordingly, a need exists for improving the jet pump for circulating refrigerant in order to increase the effectiveness of the refrigeration process.